Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
  • H01L21/2003—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate
  • H01L21/2007—Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
  • H10K59/12—Active-matrix OLED [AMOLED] displays
  • H10K59/1201—Manufacture or treatment
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/80—Manufacture or treatment specially adapted for the organic devices covered by this subclass using temporary substrates
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K77/00—Constructional details of devices covered by this subclass and not covered by groups H10K10/80, H10K30/80, H10K50/80 or H10K59/80
  • H10K77/10—Substrates, e.g. flexible substrates
  • H10K77/111—Flexible substrates
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
  • H10K2102/301—Details of OLEDs
  • H10K2102/311—Flexible OLED
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/549—Organic PV cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
  • Y10T156/10—Methods of surface bonding and/or assembly therefor
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
  • Y10T156/10—Methods of surface bonding and/or assembly therefor
  • Y10T156/1052—Methods of surface bonding and/or assembly therefor with cutting, punching, tearing or severing

Definitions

• the present invention is directed to articles and methods for processing electronic devices on flexible sheets on carriers and, more particularly to articles and methods for processing electronic devices on flexible glass sheets on glass carriers.
• display devices can be manufactured using a glass carrier laminated to one or more thin glass substrates. It is anticipated that the low permeability and improved temperature and chemical resistance of the thin glass will enable higher performance longer lifetime flexible displays.
• FPD processes require a robust bond for thin glass bound to a carrier.
• FPD processes typically involve vacuum deposition (sputtering metals, transparent conductive oxides and oxide semiconductors, Chemical Vapor Deposition (CVD) deposition of amorphous silicon, silicon nitride, and silicon dioxide, and dry etching of metals and insulators), thermal processes (including -300 - 400°C CVD deposition, up to 600°C p-Si crystallization, 350 - 450°C oxide semiconductor annealing, up to 650°C dopant annealing, and -200 - 350°C contact annealing), acidic etching (metal etch, oxide semiconductor etch), solvent exposure (stripping photoresist, deposition of polymer encapsulation), and ultrasonic exposure (in solvent stripping of photoresist and aqueous cleaning, typically in alkaline solutions).
• vacuum deposition sputtering metals, transparent conductive oxides and oxide semiconductors, Chemical Vap
• Adhesive wafer bonding has been widely used in Micromechanical Systems (MEMS) and semiconductor processing for back end steps where processes are less harsh.
• MEMS Micromechanical Systems
• Commercial adhesives by Brewer Science and Henkel are typically thick polymer adhesive layers, 5 - 200 microns thick. The large thickness of these layers creates the potential for large amounts of volatiles, trapped solvents, and adsorbed species to contaminate FPD processes. These materials thermally decompose and outgas above ⁇ 250°C. The materials also may cause contamination in downstream steps by acting as a sink for gases, solvents and acids which can outgas in subsequent processes.
• US Provisional Application Serial No. 61/596,727 filed on February 8, 2012, entitled Processing Flexible Glass with a Carrier discloses that the concepts therein involve bonding a thin sheet, for example, a flexible glass sheet, to a carrier initially by van der Waals forces, then increasing the bond strength in certain regions while retaining the ability to remove portions of the thin sheet after processing the thin sheet/carrier to form devices (for example, electronic or display devices, components of electronic or display devices, organic light emitting device (OLED) materials, photo-voltaic (PV) structures, or thin film transistors), thereon.
• devices for example, electronic or display devices, components of electronic or display devices, organic light emitting device (OLED) materials, photo-voltaic (PV) structures, or thin film transistors
• At least a portion of the thin glass is bonded to a carrier such that there is prevented device process fluids from entering between the thin sheet and carrier, whereby there is reduced the chance of contaminating downstream processes, i.e., the bonded seal portion between the thin sheet and carrier is hermetic, and in some preferred
• this seal encompasses the outside of the article thereby preventing liquid or gas intrusion into or out of any region of the sealed article.
• US '727 goes on to disclose that in low temperature polysilicon (LTPS) (low temperature compared to solid phase crystallization processing which can be up to about 750°C) device fabrication processes, temperatures approaching 600°C or greater, vacuum, and wet etch environments may be used. These conditions limit the materials that may be used, and place high demands on the carrier/thin sheet. Accordingly, what is desired is a carrier approach that utilizes the existing capital infrastructure of the manufacturers, enables processing of thin glass, i.e., glass having a thickness ⁇ 0.3 mm thick, without contamination or loss of bond strength between the thin glass and carrier at higher processing temperatures, and wherein the thin glass de-bonds easily from the carrier at the end of the process.
• LTPS low temperature polysilicon
• the glass surfaces are cleaned to remove all metal, organic and particulate residues, and to leave a mostly silanol terminated surface.
• the glass surfaces are first brought into intimate contact where van der Waals and/or Hydrogen- bonding forces pull them together. With heat and optionally pressure, the surface silanol groups condense to form strong covalent Si-O-Si bonds across the interface, permanently fusing the glass pieces. Metal, organic and particulate residue will prevent bonding by obscuring the surface preventing the intimate contact required for bonding.
• a high silanol surface concentration is also required to form a strong bond as the number of bonds per unit area will be determined by the probability of two silanol species on opposing surfaces reacting to condense out water.
• Zhuravlel has reported the average number of hydro xyls per nm 2 for well hydrated silica as 4.6 to 4.9.
• Zhuravlel, L. T. The Surface Chemistry of Amorphous Silika, Zhuravlev Model, Colloids and Surfaces A: Physiochemical Engineering Aspects 173 (2000) 1-38.
• a non-bonding region is formed within a bonded periphery, and the primary manner described for forming such non-bonding area is increasing surface roughness.
• An average surface roughness of greater than 2 nm Ra can prevent glass to glass bonds forming during the elevated temperature of the bonding process.
• the articles and methods for processing thin sheets with carriers in US '727 and US '880 are able to withstand the harsh environments of FPD processing, undesirably for some applications, reuse of the carrier is prevented by the strong covalent bond between thin glass and glass carrier in the bonding region that is bonded by covalent, for example Si-O-Si, bonding with adhesive force -1000-2000 mJ/m 2 , on the order of the fracture strength of the glass. Prying or peeling cannot be used to separate the covalently bonded portion of the thin glass from the carrier and, thus, the entire thin sheet cannot be removed from the carrier. Instead, the non-bonded areas with the devices thereon are scribed and extracted leaving a bonded periphery of the thin glass sheet on the carrier.
• Such controlled bonding can be utilized to create an article having a re-usable carrier, or alternately an article having patterned areas of controlled bonding and covalent bonding between a carrier and a sheet.
• the present disclosure provides surface modification layers (including various materials and associated surface heat treatments), that may be provided on the thin sheet, the carrier, or both, to control both room-temperature van der Waals, and/or hydrogen, bonding and high temperature covalent bonding between the thin sheet and carrier.
• the room-temperature bonding may be controlled so as to be sufficient to hold the thin sheet and carrier together during vacuum processing, wet processing, and/or ultrasonic cleaning processing.
• the high temperature covalent bonding may be controlled so as to prevent a permanent bond between the thin sheet and carrier during high temperature processing, as well as maintain a sufficient bond to prevent delamination during high temperature processing.
• the surface modification layers may be used to create various controlled bonding areas (wherein the carrier and sheet remain sufficiently bonded through various processes, including vacuum processing, wet processing, and/or ultrasonic cleaning processing), together with covalent bonding regions to provide for further processing options, for example, maintaining hermeticity between the carrier and sheet even after dicing the article into smaller pieces for additional device processing.
• some surface modification layers provide control of the bonding between the carrier and sheet while, at the same time, reduce outgassing emissions during the harsh conditions in an FPD (for example LTPS) processing
• FIG. 1 is a schematic side view of an article having carrier bonded to a thin sheet with a surface modification layer therebetween.
• FIG. 2 is an exploded and partially cut-away view of the article in FIG. 1.
• FIG. 3 is a graph of surface hydroxyl concentration on silica as a function of temperature.
• FIG. 4 is a graph of the surface energy of an SCI -cleaned sheet of glass as a function annealing temperature.
• FIG. 5 is a graph of the surface energy of a thin fluoropolymer film deposited on a sheet of glass as a function of the percentage of one of the constituent materials from which the film was made.
• FIG. 6 is a schematic top view of a thin sheet bonded to a carrier by bonding areas.
• FIG. 7 is a schematic view of a testing setup
• FIG. 8 is a collection of graphs of surface energy (of different parts of the test setup of FIG. A) versus time for a variety of materials under different conditions.
• FIG. 9 is a graph of change in % bubble area versus temperature for a variety of materials.
• FIG. 10 is another graph of change in % bubble area versus temperature for a variety of materials.
• Ranges can be expressed herein as from “about” one particular value, and/or to "about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
• the present disclosure sets forth articles and methods for enabling a thin sheet to be processed through the harsh environment of the FPD processing lines, including high temperature processing— wherein high temperature processing is processing at a temperature > 400°C, and may vary depending upon the type of device being made, for example, temperatures up to about 450°C as in amorphous silicon or amorphous indium gallium zinc oxide (IGZO) backplane processing, up to about 500-550°C as in crystalline IGZO processing, or up to about 600-650°C as is typical in LTPS processes— and yet still allows the thin sheet to be easily removed from the carrier without damage (for example, wherein one of the carrier and the thin sheet breaks or cracks into two or more pieces) to the thin sheet or carrier, whereby the carrier may be reused.
• high temperature processing is processing at a temperature > 400°C, and may vary depending upon the type of device being made, for example, temperatures up to about 450°C as in amorphous silicon or amorphous indium gallium zinc oxide (IGZO
• a glass article 2 has a thickness 8, and includes a carrier 10 having a thickness 18, a thin sheet 20 (i.e., one having a thickness of ⁇ 300 microns, including but not limited to thicknesses of, for example, 10-50 microns, 50-100 microns, 100- 150 microns, 150-300 microns, 300, 250, 200 190, 180, 170, 160, 150 140, 130, 120 110 100, 90, 80, 70, 60, 50, 40 30, 20, or 10, microns) having a thickness 28, and a surface
• the glass article 2 is designed to allow the processing of thin sheet 20 in equipment designed for thicker sheets (i.e., those on the order of > .4mm, e.g., .4 mm, .5 mm, .6 mm, .7 mm, .8 mm, .9 mm, or 1.0 mm) although the thin sheet 20 itself is ⁇ 300 microns. That is, the thickness 8, which is the sum of thicknesses 18, 28, and 38, is designed to be equivalent to that of the thicker sheet for which a piece of equipment— for example, equipment designed to dispose electronic device components onto substrate sheets— was designed to process.
• thickness 18 would be selected as 400 microns, assuming that thickness 38 is negligible. That is, the surface modification layer 30 is not shown to scale; instead, it is greatly exaggerated for sake of illustration only. Additionally, the surface modification layer is shown in cut-away. In actuality, the surface modification layer would be disposed uniformly over the bonding surface 14 when providing a reusable carrier.
• thickness 38 will be on the order of nanometers, for example 0.1 to 2.0, or up to 10 nm, and in some instances may be up to 100 nm. The thickness 38 may be measured by ellipsometer.
• the presence of a surface modification layer may be detected by surface chemistry analysis, for example by ToF Sims mass spectrometry. Accordingly, the contribution of thickness 38 to the article thickness 8 is negligible and may be ignored in the calculation for determining a suitable thickness 18 of carrier 10 for processing a given thin sheet 20 having a thickness 28. However, to the extent that surface modification layer 30 has any significant thickness 38, such may be accounted for in determining the thickness 18 of a carrier 10 for a given thickness 28 of thin sheet 20, and a given thickness for which the processing equipment was designed.
• Carrier 10 has a first surface 12, a bonding surface 14, a perimeter 16, and thickness 18. Further, the carrier 10 may be of any suitable material including glass, for example.
• the carrier need not be glass, but instead can be ceramic, glass-ceramic, or metal (as the surface energy and/or bonding may be controlled in a manner similar to that described below in connection with a glass carrier). If made of glass, carrier 10 may be of any suitable composition including alumino-silicate, boro-silicate, alumino-boro-silicate, soda-lime- silicate, and may be either alkali containing or alkali-free depending upon its ultimate application.
• Thickness 18 may be from about 0.2 to 3 mm, or greater, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7, 1.0, 2.0, or 3 mm, or greater, and will depend upon the thickness 28, and thickness 38 when such is non-negligible, as noted above.
• the carrier 10 may be made of one layer, as shown, or multiple layers (including multiple thin sheets) that are bonded together. Further, the carrier may be of a Gen 1 size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• the thin sheet 20 has a first surface 22, a bonding surface 24, a perimeter 26, and thickness 28. Perimeters 16 and 26 may be of any suitable shape, may be the same as one another, or may be different from one another. Further, the thin sheet 20 may be of any suitable material including glass, ceramic, or glass-ceramic, for example. When made of glass, thin sheet 20 may be of any suitable composition, including alumino-silicate, boro- silicate, alumino-boro-silicate, soda-lime-silicate, and may be either alkali containing or alkali free depending upon its ultimate application. The coefficient of thermal expansion of the thin sheet could be matched relatively closely with that of the carrier to prevent warping of the article during processing at elevated temperatures.
• the thickness 28 of the thin sheet 20 is 300 microns or less, as noted above.
• the thin sheet may be of a Gen 1 size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• Gen 1 size or larger for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• Gen 2 may be of a Gen 1 size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• FPD flat panel display
• processing may include wet ultrasonic, vacuum, and high temperature (e.g., > 400°C), processing.
• the temperature may be > 500°C, or > 600°C, and up to 650°C.
• the bonding surface 14 In order to survive the harsh environment in which article 2 will be processed, as during FPD manufacture for example, the bonding surface 14 should be bonded to bonding surface 24 with sufficient strength so that the thin sheet 20 does not separate from carrier 10. And this strength should be maintained through the processing so that the thin sheet 20 does not separate from the carrier 10 during processing. Further, to allow the thin sheet 20 to be removed from carrier 10 (so that carrier 10 may be reused), the bonding surface 14 should not be bonded to bonding surface 24 too strongly either by the initially designed bonding force, and/or by a bonding force that results from a modification of the initially designed bonding force as may occur, for example, when the article undergoes processing at high temperatures, e.g., temperatures of > 400°C.
• the surface modification layer 30 may be used to control the strength of bonding between bonding surface 14 and bonding surface 24 so as to achieve both of these objectives.
• the controlled bonding force is achieved by controlling the contributions of van der Waals (and/or hydrogen bonding) and covalent attractive energies to the total adhesion energy which is controlled by modulating the polar and non-polar surface energy components of the thin sheet 20 and the carrier 10.
• This controlled bonding is strong enough to survive FPD processing (including wet, ultrasonic, vacuum, and thermal processes including temperatures > 400°C, and in some instances, processing temperatures of > 500°C, or > 600°C, and up to 650°C.) and remain de-bondable by application of sufficient separation force and yet by a force that will not cause catastrophic damage to the thin sheet 20 and/or the carrier 10.
• FPD processing including wet, ultrasonic, vacuum, and thermal processes including temperatures > 400°C, and in some instances, processing temperatures of > 500°C, or > 600°C, and up to 650°C.
• the surface modification layer 30 is shown as a solid layer between thin sheet 20 and carrier 10, such need not be the case.
• the layer 30 may be on the order of 0.1 to 2 nm thick, and may not completely cover every bit of the bonding surface 14.
• the coverage may be ⁇ 100%, from 1% to 100%, from 10% to 100%, from 20% to 90%, or from 50% to 90%.
• the layer 30 may be up to 10 nm thick, or in other embodiments even up to 100 nm thick.
• the surface modification layer 30 may be considered to be disposed between the carrier 10 and thin sheet 20 even though it may not contact one or the other of the carrier 10 and thin sheet 20.
• an important aspect of the surface modification layer 30 is that it modifies the ability of the bonding surface 14 to bond with bonding surface 24, thereby controlling the strength of the bond between the carrier 10 and the thin sheet 20.
• the material and thickness of the surface modification layer 30, as well as the treatment of the bonding surfaces 14, 24 prior to bonding, can be used to control the strength of the bond (energy of adhesion) between carrier 10 and thin sheet 20.
• a fully covalently bonded wafer pair as achieved during high temperature processing (on the order of 400 to 800 °C) has adhesion energy of- 1000- 3000 mJ/m 2 which does not allow separation of the bonded surfaces; instead, the two wafers act as a monolith.
• the adhesion energy would be that of the coating material, and would be very low leading to low or no adhesion between the bonding surfaces 14, 24, whereby the thin sheet 20 would not be able to be processed on carrier 10.
• the inventors have found various manners of providing a surface modification layer 30 leading to an adhesion energy that is between these two extremes, and such that there can be produced a controlled bonding that is sufficient enough to maintain a pair of glass substrates (for example a glass carrier 10 and a thin glass sheet 20) bonded to one another through the rigors of FPD processing but also of a degree that (even after high temperature processing of, e.g. > 400°C) allows the detachment of the thin sheet 20 from the carrier 10 after processing is complete.
• the detachment of the thin sheet 20 from the carrier 10 can be performed by mechanical forces, and in such a manner that there is no catastrophic damage to at least the thin sheet 20, and preferably also so that there is no catastrophic damage to the carrier 10.
• Equation (5) describes that the adhesion energy is a function of four surface energy parameters plus the covalent and electrostatic energy, if any.
• An appropriate adhesion energy can be achieved by judicious choice of surface modifiers, i.e., of surface modification layer 30, and/or thermal treatment of the surfaces prior to bonding.
• the appropriate adhesion energy may be attained by the choice of chemical modifiers of either one or both of bonding surface 14 and bonding surface 24, which in turn control both the van der Waal (and/or hydrogen bonding, as these terms are used
• adhesion energy as well as the likely covalent bonding adhesion energy resulting from high temperature processing (e.g., on the order of > 400°C).
• high temperature processing e.g., on the order of > 400°C.
• Control of the initial van der Waals (and/or hydrogen) bonding at room temperature is performed so as to provide a bond of one surface to the other to allow vacuum and or spin-rinse-dry (SRD) type processing, and in some instances also an easily formed bond of one surface to the other— wherein the easily formed bond can be performed at room temperature without application of externally applied forces over the entire area of the thin sheet 20 as is done in pressing the thin sheet 20 to the carrier 10 with a squeegee, or with a reduced pressure environment. That is, the initial van der Waals bonding provides at least a minimum degree of bonding holding the thin sheet and carrier together so that they do not separate if one is held and the other is allowed to be subjected to the force of gravity.
• SRD spin-rinse-dry
• the initial van der Walls (and/or hydrogen) bonding will be of such an extent that the article may also go through vacuum, SRD, and ultrasonic processing without the thin sheet delaminating from the carrier.
• This precise control of both van der Waal (and/or hydrogen bonding) and covalent interactions at appropriate levels via surface modification layer 30 (including the materials from which it is made and/or the surface treatment of the surface to which it is applied), and/or by heat treatment of the bonding surfaces prior to bonding them together achieves the desired adhesion energy that allows thin sheet 20 to bond with carrier 10 throughout FPD style processing, while at the same time, allowing the thin sheet 20 to be separated (by an appropriate force avoiding damage to the thin sheet 20 and/or carrier) from the carrier 10 after FPD style processing.
• FPD processing for example p-Si and oxide TFT fabrication typically involve thermal processes at temperatures above 400°C, above 500°C, and in some instances at or above 600°C, up to 650°C which would cause glass to glass bonding of a thin glass sheet 20 with a glass carrier 10 in the absence of surface modification layer 30. Therefore controlling the formation of Si-O-Si bonding leads to a reusable carrier.
• One method of controlling the formation of Si-O-Si bonding at elevated temperature is to reduce the concentration of surface hydro xyls on the surfaces to be bonded.
• FIG. 3 which is Iler's plot (R. K. Filer: The Chemistry of Silica (Wiley- Interscience, New York, 1979) of surface hydro xyl concentration on silica as a function of temperature, the number of hydro xyls (OH groups) per square nm decreases as the temperature of the surface increases.
• heating a silica surface and by analogy a glass surface, for example bonding surface 14 and/or bonding surface 24) reduces the
• a controlled bonding area that is, a bonding area that provides a sufficient room-temperature bond between the thin sheet 20 and carrier 10 to allow the article 2 to be processed in FPD type processes (including vacuum and wet processes), and yet one that controls covalent bonding between the thin sheet 20 and carrier 10 (even at elevated temperatures > 400°C) so as to allow the thin sheet 20 to be removed from the carrier 10 (without damage to at least the thin sheet, and preferably without damage to the carrier also) after the article 2 has finished high temperature processing, for example, FPD type processing or LTPS processing.
• FPD type processes including vacuum and wet processes
• covalent bonding between the thin sheet 20 and carrier 10 even at elevated temperatures > 400°C
• the following five tests were used to evaluate the likelihood that a particular bonding surface preparation and surface modification layer 30 would allow a thin sheet 20 to remain bonded to a carrier 10 throughout FPD processing, while allowing the thin sheet 20 to be removed from the carrier 10 (without damaging the thin sheet 20 and/ or the carrier 10) after such processing (including processing at temperatures > 400°C).
• the tests were performed in order, and a sample progressed from one test to the next unless there was failure of the type that would not permit the subsequent testing.
• Vacuum testing Vacuum compatibility testing was performed in an STS Multiplex PECVD loadlock (available from SPTS, Newport, UK) -The loadlock was pumped by an Ebara A10S dry pump with a soft pump valve (available from Ebara
• Failure as indicated by a notation of "F” in the "SRD” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) movement of the thin sheet relative to the carrier (as determined by visual observation with the naked eye - samples were photographed before and after testing, wherein failure was deemed to have occurred if there was a movement of bond defects, e.g., bubbles, or if edges debonded, or if there was a movement of the thin sheet on the carrier); or (d) penetration of water under the thin sheet (as determined by visual inspection
• Failure as indicated by a notation of "F” in the "400°C” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) increased adhesion between the carrier and the thin sheet whereby such increased adhesion prevents debonding (by insertion of a razor blade between the thin sheet and carrier, and/or by sticking a piece of KaptonTM tape, 1" wide x 6" long with 2-3" attached to 100mm square thin glass ( K102 series from Saint Gobain Performance Plastic, Hoosik Y) to the thin sheet and pulling on the
• 600°C process compatibility testing was performed using an Alwin21 Accuthermo610 RTP.
• a carrier with a thin sheet was heated in a chamber cycled from room temperature to 600°C at 9.5°C/min, held at 600°C for 600seconds, and then cooled at l °C/min to 300°C. The carrier and thin sheet were then allowed to cool to room temperature.
• Failure as indicated by a notation of "F" in the "600°C” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) increased adhesion between the carrier and the thin sheet whereby such increased adhesion prevents debonding (by insertion of a razor blade between the thin sheet and carrier, and/or by sticking a piece of KaptonTM tape as described above to the thin sheet and pulling on the tape) of the thin sheet from the carrier without damaging the thin sheet or the carrier, wherein a failure was deemed to have occurred if there was damage to the
• Ultrasonic testing was performed by cleaning the article in a four tank line, wherein the article was processed in each of the tanks sequentially from tank #1 to tank #4.
• Tank dimensions, for each of the four tanks, were 18.4"L x 10"W x 15"D.
• Two cleaning tanks (#1 and #2) contained l%Semiclean KG available from
• the cleaning tank #1 was agitated with a NEY prosonik 2 104 kHz ultrasonic generator (available from Blackstone-NEY Ultrasonics, Jamestown, NY), and the cleaning tank #2 was agitated with a NEY prosonik 2 104 kHz ultrasonic generator.
• Two rinse tanks (tank #3 and tank #4) contained DI water at 50°C.
• the rinse tank #3 was agitated by NEY sweepsonik 2D 72 kHz ultrasonic generator and the rinse tank #4 was agitated by a NEY sweepsonik 2D 104 kHz ultrasonic generator.
• a typical cleaning process for preparing glass for bonding is the SCI cleaning process where the glass is cleaned in a dilute hydrogen peroxide and base (commonly ammonium hydroxide, but tetramethylammonium hydroxide solutions for example JT Baker JTB-100 or JTB-1 11 may also be used). Cleaning removes particles from the bonding surfaces, and makes the surface energy known, i.e., it provides a base-line of surface energy.
• the manner of cleaning need not be SCI , other types of cleaning may be used, as the type of cleaning is likely to have only a very minor effect on the silanol groups on the surface. The results for various tests are set forth below in Table 1.
• a strong but separable initial, room temperature or van der Waal and/or Hydrogen- bond was created by simply cleaning a thin glass sheet of 100mm square x 100 micron thick, and a glass carrier 150mm diameter single mean flat (SMF) wafer 0.50 or 0.63 mm thick, each comprising Eagle XG® display glass (an alkali-free, alumino-boro-silicate glass, having an average surface roughness Ra on the order of 0.2 nm, available from Corning
• SMF single mean flat
• the above-described preparation of the bonding surfaces 14, 24 via heating alone and then bonding of the carrier 10 and the thin sheet 12, without a surface modification layer 30, is not a suitable controlled bond for FPD processes wherein the temperature will be > 400°C.
• Hydroxyl reduction as by heat treatment for example, and a surface modification layer 30 may be used together to control the interaction of bonding surfaces 14, 24.
• the bonding energy both van der Waals and/or Hydrogen-bonding at room temperature due to the polar/dispersion energy components, and covalent bonding at high temperature due to the covalent energy component
• the bonding energy of the bonding surfaces 14, 24 can be controlled so as to provide varying bond strength from that wherein room-temperature bonding is difficult, to that allowing easy room-temperature bonding and separation of the bonding surfaces after high temperature processing, to that which— after high temperature processing— prevents the surfaces from separating without damage.
• a re-usable carrier for FPD processes and the like wherein process temperatures > 500°C, or > 600°C, and up to 650°C, may be achieved
• the surface modification layer may be used to control room temperature bonding by which the thin sheet and carrier are initially put together, whereas the reduction of hydro xyl groups on the surface (as by heating the surface, or by reaction of the hydroxyl groups with the surface modification layer, for example) may be used to control the covalent bonding, particularly that at high temperatures.
• a material for the surface modification layer 30 may provide a bonding surface 14, 24 with an energy (for example, and energy ⁇ 40 mJ/m 2 , as measured for one surface, and including polar and dispersion components) whereby the surface produces only weak bonding.
• an energy for example, and energy ⁇ 40 mJ/m 2 , as measured for one surface, and including polar and dispersion components
• HMDS hexamethyldisilazane
• TMS trimethylsilyl
• HMDS as a surface modification layer may be used together with surface heating to reduce the hydroxyl concentration to control both room temperature and high temperature bonding.
• HMDS treatment of both thin glass and carrier creates a weakly bonded surface which is challenging to bond at room temperature with van der Waals (and/or hydrogen bonding) forces. Mechanical force is applied to bond the thin glass to the carrier. As shown in example 2a of Table 2, this bonding is sufficiently weak that deflection of the carrier is observed in vacuum testing and SRD processing, bubbling (likely due to outgassing) was observed in 400°C and 600°C thermal processes, and particulate defects were observed after ultrasonic processing.
• HMDS treatment of just one surface creates stronger room temperature adhesion which survives vacuum and SRD processing.
• FIG. 4 shows the surface energy of an Eagle XG® display glass carrier after annealing, and after HMDS treatment. Increased annealing temperature prior to HMDS exposure increases the total (polar and dispersion) surface energy (line 402) after HMDS exposure by increasing the polar contribution (line 404).
• the thin glass sheet was heated at a temperature of 150°C in a vacuum for one hour prior to bonding with the non-heat-treated carrier having a coating of HMDS. This heat treatment of the thin glass sheet was not sufficient to prevent permanent bonding of the thin glass sheet to the carrier at temperatures > 400°C.
• varying the annealing temperature of the glass surface prior to HMDS exposure can vary the bonding energy of the glass surface so as to control bonding between the glass carrier and the thin glass sheet.
• the carrier was annealed at a temperature of 190°C in vacuum for 1 hour, followed by HMDS exposure to provide surface modification layer 30. Additionally, the thin glass sheet was annealed at 450°C in a vacuum for 1 hour before bonding with the carrier.
• the resulting article survived the vacuum, SRD, and 400°C tests (parts a and c, but did not pass part b as there was increased bubbling), but failed the 600°C test. Accordingly, although there was increased resistance to high temperature bonding as compared with example 2b, this was not sufficient to produce an article for processing at temperatures > 600°C (for example LTPS processing) wherein the carrier is reusable.
• the carrier was annealed at a temperature of 340°C in a vacuum for 1 hour, followed by HMDS exposure to provide surface modification layer 30. Again, the thin glass sheet was annealed at 450°C for 1 hour in a vacuum before bonding with the carrier.
• the results were similar to those for example 2c, wherein the article survived the vacuum, SRD, and 400°C tests (parts a and c, but did not pass part b as there was increased bubbling), but failed the 600 °C test.
• annealing both thin glass and carrier at 450°C in vacuum for 1 hr, followed by HMDS exposure of the carrier, and then bonding of the carrier and thin glass sheet improves the temperature resistance to permanent bonding.
• An anneal of both surfaces to 450°C prevents permanent bonding after RTP annealing at 600°C for 10 min, that is, this sample passed the 600°C processing test (parts a and c, but did not pass part b as there was increased bubbling; a similar result was found for the 400°C test).
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick
• the HMDS was applied by pulse vapor deposition in a YES-5 HMDS oven (available from Yield Engineering Systems, San Jose CA) and was one atomic layer thick (i.e., about 0.2 to 1 nm), although the surface coverage may be less than one monolayer, i.e., some of the surface hydroxyls are not covered by the HMDS as noted by Maciel and discussed above.
• each of the carriers and thin sheets were cleaned using an SCI process prior to heat treating or any subsequent HMDS treatment.
• a comparison of example 2a with example 2b shows that the bonding energy between the thin sheet and the carrier can be controlled by varying the number of surfaces which include a surface modification layer. And controlling the bonding energy can be used to control the bonding force between two bonding surfaces.
• a comparison of examples 2b-2e shows that the bonding energy of a surface can be controlled by varying the parameters of a heat treatment to which the bonding surface is subjected before application of a surface modification material. Again, the heat treatment can be used to reduce the number of surface hydroxyls and, thus, control the degree of covalent bonding, especially that at high temperatures.
• a reusable carrier can also be created if one or both bonding surfaces are modified to create a moderate bonding force with a surface modification layer that either covers, or sterically hinders species for example hydroxyls to prevent the formation at elevated temperature of strong permanent covalent bonds between carrier and thin sheet.
• a surface modification layer that either covers, or sterically hinders species for example hydroxyls to prevent the formation at elevated temperature of strong permanent covalent bonds between carrier and thin sheet.
• One way to create a tunable surface energy, and cover surface hydroxyls to prevent formation of covalent bonds is deposition of plasma polymer films, for example fluoropolymer films.
• Plasma polymerization deposits a thin polymer film under atmospheric or reduced pressure and plasma excitation (DC or RF parallel plate, Inductively Coupled Plasma (ICP) Electron Cyclotron Resonance (ECR) downstream microwave or RF plasma) from source gases for example fluorocarbon sources (including CF4, CHF3, C2F6, C3F6, C2F2, CH3F, C4F8, chlorofluoro carbons, or hydrochlorofluoro carbons), hydrocarbons for example alkanes (including methane, ethane, propane, butane), alkenes (including ethylene, propylene), alkynes (including acetylene), and aromatics (including benzene, toluene), hydrogen, and other gas sources for example SF6.
• Plasma polymerization creates a layer of highly cross-linked material. Control of reaction conditions and source gases can be used to control the film thickness, density, and chemistry to tailor the functional groups to the desired application.
• FIG. 5 shows the total (line 502) surface energy (including polar (line 504) and dispersion (line 506) components) of plasma polymerized fluoropolymer (PPFP) films deposited from CF4-C4F8 mixtures with an Oxford ICP380 etch tool (available from Oxford Instruments, Oxfordshire UK). The films were deposited onto a sheet of Eagle XG ® glass, and spectroscopic ellipsometry showed the films to be 1 -10 nm thick. As seen from FIG. 5, glass carriers treated with plasma polymerized fluoropolymer films containing less than 40% C4F8 exhibit a surface energy >40 mJ/m 2 and produce controlled bonding between the thin glass and carrier at room temperature by van der Waal or hydrogen bonding.
• PPFP plasma polymerized fluoropolymer
• the surface modification layer of PPFP2 may be useful for some applications, as where ultrasonic processing is not necessary.
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick. Because of the small thickness in the surface modification layer, there is little risk of outgassing which can cause contamination in the device fabrication. Further, because the surface modification layer did not appear to degrade, again, there is even less risk of outgassing. Also, as indicated in Table 3, each of the thin sheets was cleaned using an SCI process prior to heat treating at 150°C for one hour in a vacuum.
• Still other materials may be used as the surface modification layer to control the room temperature and high temperature bonding forces between the thin sheet and the carrier.
• a bonding surface that can produce controlled bonding can be created by silane treating a glass carrier and/or glass thin sheet.
• Silanes are chosen so as to produce a suitable surface energy, and so as to have sufficient thermal stability for the application.
• the carrier or thin glass to be treated may be cleaned by a process for example 02 plasma or UV-ozone, and SCI or standard clean two (SC2, as is known in the art) cleaning to remove organics and other impurities (metals, for example) that would interfere with the silane reacting with the surface silanol groups.
• Washes based on other chemistries may also be used, for example, HF, or H2S04 wash chemistries.
• the carrier or thin glass may be heated to control the surface hydroxyl concentration prior to silane application (as discussed above in connection with the surface modification layer of HMDS), and/or may be heated after silane application to complete silane condensation with the surface hydroxyls.
• concentration of unreacted hydroxyl groups after silanization may be made low enough prior to bonding as to prevent permanent bonding between the thin glass and carrier at temperatures > 400°C, that is, to form a controlled bond. This approach is described below.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% dodecyltriethoxysilane (DDTS) in toluene, and annealed at 150°C in vacuum for 1 hr to complete condensation.
• DDTS treated surfaces exhibit a surface energy of 45 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the DDTS surface modification layer thereon. This article survived wet and vacuum process tests but did not survive thermal processes over 400 °C without bubbles forming under the carrier due to thermal decomposition of the silane.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% 3,3,3, trifluoropropyltritheoxysilane (TFTS) in toluene, and annealed at 150°C in vacuum for 1 hr to complete condensation.
• TFTS treated surfaces exhibit a surface energy of 47 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the TFTS surface modification layer thereon. This article survived the vacuum, SRD, and 400°C process tests without permanent bonding of the glass thin sheet to the glass carrier.
• the 600°C test produced bubbles forming under the carrier due to thermal decomposition of the silane. This was not unexpected because of the limited thermal stability of the propyl group. Although this sample failed the 600°C test due to the bubbling, the material and heat treatment of this example may be used for some applications wherein bubbles and the adverse effects thereof, for example reduction in surface flatness, or increased waviness, can be tolerated.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% phenyltriethoxysilane (PTS) in toluene, and annealed at 200°C in vacuum for 1 hr to complete condensation.
• PTS treated surfaces exhibit a surface energy of 54 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the PTS surface modification layer. This article survived the vacuum, SRD, and thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% diphenyldiethoxysilane (DPDS) in toluene, and annealed at 200°C in vacuum for 1 hr to complete condensation.
• DPDS treated surfaces exhibit a surface energy of 47 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the DPDS surface modification layer. This article survived the vacuum and SRD tests, as well as thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier
• a glass carrier having its bonding surface 02 plasma and SCI treated was then treated with 1% 4-pentafluorophenyltriethoxysilane (PFPTS) in toluene, and annealed at 200°C in vacuum for 1 hr to complete condensation.
• PFPTS treated surfaces exhibit a surface energy of 57 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400° C in a vacuum for one hour) was bonded to the carrier bonding surface having the PFPTS surface modification layer. This article survived the vacuum and SRD tests, as well as thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier.
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick.
• the silane layers were self-assembled monolayers (SAM), and thus were on the order of less than about 2 nm thick.
• SAM was created using an organosilane with an aryl or alkyl non-polar tail and a mono, di, or tri-alkoxide head group. These react with the silnaol surface on the glass to directly attach the organic functionality. Weaker interactions between the non-polar head groups organize the organic layer.
• each of the glass thin sheets was cleaned using an SCI process prior to heat treating at 400 °C for one hour in a vacuum.
• each carrier had a surface energy above 40 mJ/m 2 , which facilitated initial room temperature bonding so that the article survived vacuum and SRD processing.
• examples 4a and 4b did not pass 600°C processing test.
• One use of controlled bonding via surface modification layers is to provide reuse of the carrier in an article undergoing processes requiring a temperature > 600°C, as in LTPS processing, for example.
• Surface modification layers including the materials and bonding surface heat treatments
• these surface modification layers may be used to provide reuse of the carrier under such temperature conditions.
• these surface modification layers may be used to modify the surface energy of the area of overlap between the bonding areas of the thin sheet and carrier, whereby the entire thin sheet may be separated from the carrier after processing.
• the thin sheet may be separated all at once, or may be separated in sections as, for example, when first removing devices produced on portions of the thin sheet and thereafter removing the remaining portions to clean the carrier for reuse.
• the carrier can be reused as is by simply by placing another thin sheet thereon.
• the carrier may be cleaned and once again prepared to carry a thin sheet by forming a surface modification layer anew. Because the surface modification layers prevent permanent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• these surface modification layers may control bonding surface energy during processing at temperatures > 600°C, they may also be used to produce a thin sheet and carrier combination that will withstand processing at lower temperatures, and may be used in such lower temperature applications to control bonding. Moreover, where the thermal processing of the article will not exceed 400°C, surface modification layers as exemplified by the examples 2c, 2d, 4b may also be used in this same manner.
• a second use of controlled bonding via surface modification layers is to provide a controlled bonding area, between a glass carrier and a glass thin sheet. More specifically, with the use of the surface modification layers an area of controlled bonding can be formed wherein a sufficient separation force can separate the thin sheet portion from the carrier without damage to either the thin sheet or the carrier caused by the bond, yet there is maintained throughout processing a sufficient bonding force to hold the thin sheet relative to the carrier.
• a glass thin sheet 20 may be bonded to a glass carrier 10 by a bonded area 40. In the bonded area 40, the carrier 10 and thin sheet 20 are covalently bonded to one another so that they act as a monolith.
• controlled bonding areas 50 having perimeters 52, wherein the carrier 10 and thin sheet 20 are connected, but may be separated from one another, even after high temperature processing, e.g. processing at temperatures > 600°C. Although ten controlled bonding areas 50 are shown in FIG. 6, any suitable number, including one, may be provided.
• the surface modification layers 30, including the materials and bonding surface heat treatments, as exemplified by the examples 2a, 2e, 3a, 3b, 4c, 4d, and 4e, above, may be used to provide the controlled bonding areas 50 between the carrier 10 and the thin sheet 20. Specifically, these surface modification layers may be formed within the perimeters 52 of controlled bonding areas 50 either on the carrier 10 or on the thin sheet 20.
• the article 2 when the article 2 is processed at high temperature, either to form covalent bonding in the bonding area 40 or during device processing, there can be provided a controlled bond between the carrier 10 and the thin sheet 20 within the areas bounded by perimeters 52 whereby a separation force may separate (without catastrophic damage to the thin sheet or carrier) the thin sheet and carrier in this region, yet the thin sheet and carrier will not delaminate during processing, including ultrasonic processing.
• the controlled bonding of the present application as provided by the surface modification layers and any associated heat treatments, is thus able to improve upon the carrier concept in US '727.
• This problem can be eliminated by minimizing the gap between the thin glass and the carrier and by providing sufficient adhesion, or controlled bonding between the carrier 20 and thin glass 10 in these areas 50.
• Surface modification layers including materials and any associated heat treatments as exemplified by examples 2a, 2e, 3a, 3b, 4c, 4d, and 4e) of the bonding surfaces control the bonding energy so as to provide a sufficient bond between the thin sheet 20 and carrier 10 to avoid these unwanted vibrations in the controlled bonding region.
• the portions of thin sheet 20 within the perimeters 52 may simply be separated from the carrier 10 after processing and after separation of the thin sheet along perimeters 57.
• the surface modification layers control bonding energy to prevent permanent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• these surface modification layers may control bonding surface energy during processing at temperatures > 600°C, they may also be used to produce a thin sheet and carrier combination that will withstand processing at lower temperatures, and may be used in such lower temperature applications.
• surface modification layers as exemplified by the examples 2c, 2d, 4b may also be used— in some instances, depending upon the other process requirements— in this same manner to control bonding surface energy.
• a third use of controlled bonding via surface modification layers is to provide a bonding area between a glass carrier and a glass thin sheet.
• a glass thin sheet 20 may be bonded to a glass carrier 10 by a bonded area 40.
• the bonded area 40, the carrier 10 and thin sheet 20 may be covalently bonded to one another so that they act as a monolith.
• controlled bonding areas 50 having perimeters 52, wherein the carrier 10 and thin sheet 20 are bonded to one another sufficient to withstand processing, and still allow separation of the thin sheet from the carrier even after high temperature processing, e.g. processing at temperatures > 600°C.
• surface modification layers 30 including materials and bonding surface heat treatments as exemplified by the examples la, lb, lc, 2b, 2c, 2d, 4a, and 4b above, may be used to provide the bonding areas 40 between the carrier 10 and the thin sheet 20.
• these surface modification layers and heat treatments may be formed outside of the perimeters 52 of controlled bonding areas 50 either on the carrier 10 or on the thin sheet 20.
• the carrier and the thin sheet 20 will bond to one another within the bonding area 40 outside of the areas bounded by perimeters 52. Then, during extraction of the desired parts 56 having perimeters 57, when it is desired to dice the thin sheet 20 and carrier 10, the article may be separated along lines 5 because these surface modification layers and heat treatments covalently bond the thin sheet 20 with the carrier 10 so they act as a monolith in this area. Because the surface modification layers provide permanent covalent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• thermal processing of the article, or of the initial formation of the bonding area 40 will be > 400°C but less than 600°C
• surface modification layers as exemplified by the materials and heat treatments in example 4a may also be used in this same manner.
• the carrier 10 and thin sheet 20 may be bonded to one another by controlled bonding via various surface modification layers described above. Additionally, there are controlled bonding areas 50, having perimeters 52, wherein the carrier 10 and thin sheet 20 are bonded to one another sufficient to withstand processing, and still allow separation of the thin sheet from the carrier even after high temperature processing, e.g. processing at temperatures > 600°C.
• these surface modification layers and heat treatments may be formed outside of the perimeters 52 of controlled bonding areas 50, and may be formed either on the carrier 10 or on the thin sheet 20.
• the controlled bonding areas 50 may be formed with the same, or with a different, surface modification layer as was formed in the bonding area 40.
• surface modification layers 30 including materials and bonding surface heat treatments as exemplified by the examples 2c, 2d, 2e, 3a, 3b, 4b, 4c, 4d, 4e, above, may be used to provide the bonding areas 40 between the carrier 10 and the thin sheet 20.
• non-bonding regions in areas 50, wherein the non-bonding regions may be areas of increased surface roughness as described in US '727, or may be provided by surface modification layers as exemplified by example 2 a.
• a fifth use of the controlled bonding as described herein is to make glass articles— including those having a carrier and a thin sheet bonded thereto— which are, in turn, used to make electronic devices, for example, TFTs, OLEDs (including an organic light emitting material), PV devices, touch sensors, and displays.
• a re-usable carrier as described above for example, may be used.
• a glass article having bonded and controlled bonding areas as described above for example, may be used.
• electronic device processing equipment as is currently designed for thicker sheets may be used to process the glass article so as to dispose an electronic-device component, or part of the electronic device, onto the sheet of the article.
• the electronic device component should be disposed on the portion(s) of the thin sheet that are bonded to the carrier via the controlled bonding described above, whereby the thin sheet remains separable from the carrier even after processing to the temperatures necessary to make the electronic device.
• the device processing may include processing at temperatures of > 400°C, > 500°C, > 600°C, or up to 650°C, for example.
• suitable surface modification layers may be chosen so that the thin sheet remains removable from the carrier— even after processing to such temperatures— without damage to at least the thin sheet, and preferably without damage to both the thin sheet and the carrier. Any number of electronic-device components may be disposed in any number of steps for doing so, until the electronic device is complete or at a suitable intermediate stage.
• the article may be assembled before the electronic device processing, or may be assembled as a part of the electronic device making process.
• the device processing may include keeping the article intact throughout the entire device processing, or may include dicing the article at one or more points in the process.
• the device processing may include forming one electronic-device component on the article, and then dicing the article into two or more portions that are then subject to further processing, i.e., disposing an additional component of the electronic device onto the sheet or onto the electronic-device component existing on the sheet from disposition in a prior step.
• the dicing step may be done so that each portion of the article includes a portion of the thin sheet that remains bonded to the carrier, or so that only a subset of the diced portions include such an arrangement. Within any of the diced portions, the entire area of the thin sheet in that portion may remain bonded to the entire area of the carrier in that portion.
• the device and the portion of the thin sheet on which it is disposed may be removed from the carrier.
• the thin sheet may be removed in its entirety, or a portion thereof may be separated from a remaining portion and that portion removed from the carrier. The removal may take place from the article in its entirety, or from one or more of the portions diced therefrom.
• Polymer adhesives used in typical wafer bonding applications are generally 10-100 microns thick and lose about 5% of their mass at or near their temperature limit.
• mass-spectrometry For such materials, evolved from thick polymer films, it is easy to quantify the amount of mass loss, or outgassing, by mass-spectrometry.
• mass-spectrometry On the other hand, it is more challenging to measure the outgassing from thin surface treatments that are on the order of 10 nm thick or less, for example the plasma polymer or self-assembled monolayer surface modification layers described above, as well as for a thin layer of pyrolyzed silicone oil.
• mass-spectrometry is not sensitive enough. There are a number of other ways to measure outgassing, however.
• a first manner of measuring small amounts of outgassing is based on surface energy measurements, and will be described with reference to FIG. 7.
• a setup as shown in FIG. 7 may be used.
• a first substrate, or carrier, 900 having the to-be- tested surface modification layer thereon presents a surface 902, i.e., a surface modification layer corresponding in composition and thickness to the surface modification layer 30 to be tested.
• a second substrate, or cover, 910 is placed so that its surface 912 is in close proximity to the surface 902 of the carrier 900, but not in contact therewith.
• the surface 912 is an uncoated surface, i.e., a surface of bare material from which the cover is made.
• Spacers 920 are placed at various points between the carrier 900 and cover 910 to hold them in spaced relation from one another.
• the spacers 920 should be thick enough to separate the cover 910 from the carrier 900 to allow a movement of material from one to the other, but thin enough so that during testing the amount of contamination from the chamber atmosphere on the surfaces 902 and 912 is minimized.
• the surface energy of bare surface 912 is measured, as is the surface energy of the surface 902, i.e., the surface of carrier 900 having the surface modification layer provided thereon.
• test article 901 is placed into a heating chamber 930, and is heated through a time-temperature cycle.
• the heating is performed at atmospheric pressure and under flowing N2 gas, i.e., flowing in the direction of arrows 940 at a rate of 2 standard liters per minute.
• changes in the surface 902 are evidenced by a change in the surface energy of surface 902.
• a change in the surface energy of surface 902 by itself does not necessarily mean that the surface modification layer has outgassed, but does indicate a general instability of the material at that temperature as its character is changing due to the mechanisms noted above, for example.
• the less the change in surface energy of surface 902 the more stable the surface modification layer.
• any material outgassed from surface 902 will be collected on surface 912 and will change the surface energy of surface 912. Accordingly, the change in surface energy of surface 912 is a proxy for outgassing of the surface modification layer present on surface 902.
• one test for outgassing uses the change in surface energy of the cover surface 912. Specifically, if there is a change in surface energy— of surface 912— of > 10 mJ/m2, then there is outgassing. Changes in surface energy of this magnitude are consistent with contamination which can lead to loss of film adhesion or degradation in material properties and device performance. A change in surface energy of ⁇ 5 mJ/m2 is close to the repeatability of surface energy measurements and inhomogeneity of the surface energy. This small change is consistent with minimal outgassing.
• the carrier 900, the cover 910, and the spacers 920 were made of Eagle XG glass, an alkali-free alumino-boro-silicate display-grade glass available from Corning Incorporated, Corning, NY, although such need not be the case.
• the carrier 900 and cover 910 were 150mm diameter 0.63mm thick.
• the carrier 910 and cover 920 will be made of the same material as carrier 10 and thin sheet 20, respectively, for which an outgassing test is desired.
• silicon spacers 0.63 mm thick, 2mm wide, and 8cm long, thereby forming a gap of 0.63 mm between surfaces 902 and 912.
• the chamber 930 was incorporated in MPT- RTP600s rapid thermal processing equipment that was cycled from room temperature to the test limit temperature at a rate of 9.2°C per minute, held at the test limit temperature for varying times as shown in the graphs as "Anneal Time", and then cooled at furnace rate to 200°C.
• the test article was removed, and after the test article had cooled to room temperature, the surface energies of each surface 902 and 912 were again measured.
• the data was collected as follows. The data point at 0 minutes shows a surface energy of 75 mJ/m2 (milli- Joules per square meter), and is the surface energy of the bare glass, i.e., there has been no time-temperature cycle yet run.
• the data point at one minute indicates the surface energy as measured after a time-temperature cycle performed as follows: the article 901 (having Material #1 used as a surface modification layer on the carrier 900 to present surface 902) was placed in a heating chamber 930 at room temperature, and atmospheric pressure; the chamber was heated to the test-limit temperature of 450°C at a rate of 9.2°C per minute, with a N2 gas flow at two standard liters per minute, and held at the test-limit temperature of 450°C for 1 minute; the chamber was then allowed to cool to 300°C at a rate of 1 °C per minute, and the article 901 was then removed from the chamber 930; the article was then allowed to cool to room temperature (without N2 flowing atmosphere); the surface energy of surface 912 was then measured and plotted as the point for 1 minute on line 1003.
• Material #1 is a CHF3 -CF4 plasma polymerized fluoropolymer. This material is consistent with the surface modification layer in example 3b, above. As shown in FIG. 8, lines 1001 and 1002 show that the surface energy of the carrier did not significantly change. Thus, this material is very stable at temperatures from 450°C to 600°C. Additionally, as shown by the lines 1003 and 1004, the surface energy of the cover did not significantly change either, i.e., the change is ⁇ 5mJ/m2. Accordingly, there was no outgassing associated with this material from 450°C to 600°C.
• Material #2 is a phenylsilane, a self-assembled monolayer (SAM) deposited form 1% toluene solution of phenyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C.
• SAM self-assembled monolayer
• Material #3 is a pentafluorophenylsilane, a SAM deposited from 1% toluene solution of pentafluorophenyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C. This material is consistent with the surface modification layer in example 4e, above. As shown in FIG. 8, lines 1301 and 1302 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and
• Material #4 is hexamethyldisilazane (HMDS) deposited from vapor in a YES HMDS oven at 140°C. This material is consistent with the surface modification layer in Example 2b, of Table 2, above. As shown in FIG. 8, lines 1401 and 1402 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and comparatively, Material #4 is somewhat less stable than Material #1. Additionally, the change in surface energy of the carrier for Material #4 is greater than that for any of Materials #2 and #3 indicating, comparatively, that Material #4 is somewhat less stable than Materials #2 and #3.
• HMDS hexamethyldisilazane
• Material #5 is Glycidoxypropylsilane, a SAM deposited from 1% toluene solution of glycidoxypropyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C. This is a comparative example material. Although there is relatively little change in the surface energy of the carrier, as shown by lines 1501 and 1502, there is significant change in surface energy of the cover as shown by lines 1503 and 1504. That is, although Material #5 was relatively stable on the carrier surface, it did, indeed outgas a significant amount of material onto the cover surface whereby the cover surface energy changed by > 10mJ/m2.
• Material #6 is DC704 a silicone coating prepared by dispensing 5 ml Dow Corning 704 diffusion pump oil tetramethyltetraphenyl trisiloxane (available from Dow Corning) onto the carrier, placing it on a 500°C hot plate in air for 8 minutes. Completion of sample preparation is noted by the end of visible smoking. After preparing the sample in the above manner, the outgassing testing described above was carried out. This is a comparative example material. As shown in FIG. 8, lines 1601 and 1602 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and comparatively, Material #6 is less stable than Material #1.
• the change in surface energy of the carrier is > 10mJ/m2, showing significant outgassing. More particularly, at the test-limit temperature of 450°C, the data point for 10 minutes shows a decrease in surface energy of about 15 mJ/m2, and even greater decrease in surface energy for the points at 1 and 5 minutes. Similarly, the change in surface energy of the cover during cycling at the 600°C test-limit temperature, the decrease in surface energy of the cover was about 25 mJ/m2 at the 10 minute data point, somewhat more at 5 minutes, and somewhat less at 1 minute. Altogether, though, a significant amount of outgassing was shown for this material over the entire range of testing.
• a second manner of measuring small amounts of outgassing is based on an assembled article, i.e., one in which a thin sheet is bonded to a carrier via a surface modification layer, and uses a change in percent bubble area to determine outgassing. That is, during heating of the article, bubbles formed between the carrier and the thin sheet indicate outgassing of the surface modification layer. As noted above in connection with the first outgassing test, it is difficult to measure outgassing of very thin surface modification layers. In this second test, the outgassing under the thin sheet may be limited by strong adhesion between the thin sheet and carrier.
• layers ⁇ 10 nm thick may still create bubbles during thermal treatment, despite their smaller absolute mass loss.
• the creation of bubbles between the thin sheet and carrier may cause problems with pattern generation, photolithography processing, and/or alignment during device processing onto the thin sheet.
• bubbling at the boundary of the bonded area between the thin sheet and the carrier may cause problems with process fluids from one process contaminating a downstream process.
• a change in % bubble area of > 5 is significant, indicative of outgassing, and is not desirable.
• a change in % bubble area of ⁇ 1 is insignificant and an indication that there has been no outgassing.
• the average bubble area of bonded thin glass in a class 1000 clean room with manual bonding is 1%.
• the %bubbles in bonded carriers is a function of cleanliness of the carrier, thin glass sheet, and surface preparation. Because these initial defects act as nucleation sites for bubble growth after heat treatment, any change in bubble area upon heat treatment less than 1% is within the variability of sample preparation.
• a commercially available desktop scanner with transparency unit (Epson Expression 10000XL Photo) was used to make a first scan image of the area bonding the thin sheet and carrier immediately after bonding. The parts were scanned using the standard Epson software using 508 dpi (50 micron/pixel) and 24 bit RGB.
• the image processing software first prepares an image by stitching, as necessary, images of different sections of a sample into a single image and removing scanner artifacts (by using a calibration reference scan performed without a sample in the scanner).
• the bonded area is then analyzed using standard image processing techniques such as thresholding, hole filling, erosion/dilation, and blob analysis.
• the newer Epson Expression 11000XL Photo may also be used in a similar manner. In transmission mode, bubbles in the bonding area are visible in the scanned image and a value for bubble area can be determined.
• the bubble area is compared to the total bonding area (i.e., the total overlap area between the thin sheet and the carrier) to calculate a % area of the bubbles in the bonding area relative to the total bonding area.
• the samples are then heat treated in a MPT-RTP600s Rapid Thermal Processing system under N2 atmosphere at test-limit temperatures of 300°C, 450°C, and 600°C, for up to 10 minutes.
• the time- temperature cycle carried out included: inserting the article into the heating chamber at room temperature and atmospheric pressure; the chamber was then heated to the test-limit temperature at a rate of 9°C per minute; the chamber was held at the test-limit temperature for 10 minutes; the chamber was then cooled at furnace rate to 200°C; the article was removed from the chamber and allowed to cool to room temperature; the article was then scanned a second time with the optical scanner.
• the % bubble area from the second scan was then calculated as above and compared with the % bubble area from the first scan to determine a change in % bubble area ( ⁇ % bubble area). As noted above, a change in bubble area of > 5% is significant and an indication of outgassing.
• a change in % bubble area was selected as the measurement criterion because of the variability in original % bubble area. That is, most surface modification layers have a bubble area of about 2% in the first scan due to handling and cleanliness after the thin sheet and carrier have been prepared and before they are bonded. However, variations may occur between materials.
• the same Materials #1-6 set forth with respect to the first outgassing test method were again used in this second outgassing test method. Of these materials, Materials #1 -4 exhibited about 2% bubble area in the first scan, whereas Materials #5 and #6 showed significantly larger bubble area, i.e., about 4%, in the first scan.
• the surface modification layer 30 of many embodiments is shown and discussed as being formed on the carrier 10, it may instead, or in addition, be formed on the thin sheet 20. That is, the materials as set forth in the examples 4 and 3 may be applied to the carrier 10, to the thin sheet 20, or to both the carrier 10 and thin sheet 20 on faces that will be bonded together.
• controlled bonding concepts have been described herein as being used with a carrier and a thin sheet, in certain circumstances they are applicable to controlling bonding between thicker sheets of glass, ceramic, or glass ceramic, wherein it may be desired to detach the sheets (or portions of them) from each other.
• the carrier may be made of other materials, for example, ceramic, glass ceramic, or metal.
• the sheet controllably bonded to the carrier may be made of other materials, for example, ceramic or glass ceramic.
• a method of making an electronic device comprising:
• the surface energy bonding the sheet to the carrier is of such a character that after subjecting the article to a temperature cycle by heating in an chamber cycled from room temperature to 600°C at a rate of 9.2 °C per minute, held at a temperature of 600°C for 10 minutes, and then cooled at 1 °C per minute to 300 °C, and then removing the article from the chamber and allowing the article to cool to room temperature, the carrier and sheet do not separate from one another if one is held and the other subjected to the force of gravity, there is no outgassing from the surface modifiation layer during the temperature cycle, and the sheet may be separated from the carrier without breaking the thinner one of the carrier and the sheet into two or more pieces;
• a method of making an electronic device comprising:
• the glass article comprising:
• the surface energy bonding the sheet to the carrier is of such a character that after subjecting the article to a temperature cycle by heating in an chamber cycled from room temperature to 600°C at a rate of 9.2 °C per minute, held at a temperature of 600°C for 10
• the carrier and sheet do not separate from one another if one is held and the other subjected to the force of gravity, there is no outgassing from the surface modification layer during the temperature cycle, and the sheet may be separated from the carrier without breaking the thinner one of the carrier and the sheet into two or more pieces;
• processing the electronic device includes processing at a temperature > 400°C.
• processing the electronic device includes processing at a temperature > 400°C.
• processing the electronic device includes processing at a temperature > 600°C.
• the method of any one of aspects 1-10 wherein the carrier without any surface modification layer has an average surface roughness Ra of ⁇ 2 nm.
• the method of any one of aspects 1-13 wherein the sheet without any surface modification layer has an average surface roughness Ra of ⁇ 2 nm.
• the surface modification layer comprises one of:
• the method of aspect 20 wherein when the surface modification layer comprises a plasma polymerized fluoropolymer, the surface modification layer is one of: plasma polymerized polytetrafluroethylene; and a plasma polymerized fluoropolymer surface modification layer deposited from a CF4-C4F8 mixture having ⁇ 40% C4F8.
• the method of aspect 20 wherein when the surface modification layer comprises an aromatic silane, the surface modification layer is one of: phenyltriethoxysilane; diphenyldiethoxysilane; and
• the method of aspect 20 wherein when the surface modification layer comprises an aromatic silane, the surface modification layer contains chlorophenyl, or fluorophenyl, silyl groups.

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• 2013
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